Priorites added to dispatch function. This is in prep for flow
control to allow dispatch functions that haven't been serviced
in awhile to be bumped up in priority when they are not serviced.

The priority of the dispatch handler is passed to the dispatch
function which can modify it in place. The new priority will be
used the next time the poll system call is executed.

main.c:
Add library accept handler at lowest priority
gmi.c:
Make gmi highest priority when adding dispatch functions
aispoll.h, aispoll.c:
Add priority to poll abstraction
Higher priority items will be serviced first

BKrev: 411dda8dXGsq4glmjj36km40YZhjCA


git-svn-id: http://svn.fedorahosted.org/svn/corosync/trunk@171 fd59a12c-fef9-0310-b244-a6a79926bd2f